# Defining Free Fall: Does Gravity Need to be the Sole Force Present?

Can a scenario be considered free fall in physics if the work done by forces other than gravity is zero, but those forces are still present? Or is it necessary for gravity to be the only force present for an object to be considered in free fall?

General Relativity:

It is safe to consider an object in free fall only when it follows a geodesic path. If the work done by the other forces sums to zero, then the object in question remains along its geodesic path.

This is really just another way of saying that the net 4-force must equal zero.

Newtonian Gravity:

For Newtonian gravity, you can just consider the net 3-force (force with three components, as taught in intro level physics) since no 4-force is defined. That is, if the sum of the non-gravitational forces equals zero, then it's in free fall.

That all being said, it's often okay to approximate. We may choose to neglect certain forces if they aren't expected to have a significant impact. For example, neglecting air drag when the velocity of the object is low, its cross-section is small, or the medium is highly diffuse.